<template>
	<span>
		{{ displayValue }}
	</span>
</template>
<script>
import { requestAnimationFrame, cancelAnimationFrame } from './requestAnimationFrame.js';
export default {
	props: {
		startVal: {
			type: Number,
			required: false,
			default: 0,
		},
		endVal: {
			type: Number,
			required: false,
			default: 2017,
		},
		duration: {
			type: Number,
			required: false,
			default: 3000,
		},
		autoplay: {
			type: Boolean,
			required: false,
			default: true,
		},
		decimals: {
			type: Number,
			required: false,
			default: 0,
			validator(value) {
				return value >= 0;
			},
		},
		decimal: {
			type: String,
			required: false,
			default: '.',
		},
		separator: {
			type: String,
			required: false,
			default: ',',
		},
		prefix: {
			type: String,
			required: false,
			default: '',
		},
		suffix: {
			type: String,
			required: false,
			default: '',
		},
		useEasing: {
			type: Boolean,
			required: false,
			default: true,
		},
		easingFn: {
			type: Function,
			default(t, b, c, d) {
				return (c * (-Math.pow(2, (-10 * t) / d) + 1) * 1024) / 1023 + b;
			},
		},
	},
	data() {
		return {
			localStartVal: this.startVal,
			displayValue: this.formatNumber(this.startVal),
			printVal: null,
			paused: false,
			localDuration: this.duration,
			startTime: null,
			timestamp: null,
			remaining: null,
			rAF: null,
		};
	},
	computed: {
		countDown() {
			return this.startVal > this.endVal;
		},
	},
	watch: {
		startVal() {
			if (this.autoplay) {
				this.start();
			}
		},
		endVal() {
			if (this.autoplay) {
				this.start();
			}
		},
	},
	mounted() {
		if (this.autoplay) {
			this.start();
		}
		this.$emit('mountedCallback');
	},
	methods: {
		start() {
			this.localStartVal = this.startVal;
			this.startTime = null;
			this.localDuration = this.duration;
			this.paused = false;
			this.rAF = requestAnimationFrame(this.count);
		},
		pauseResume() {
			if (this.paused) {
				this.resume();
				this.paused = false;
			} else {
				this.pause();
				this.paused = true;
			}
		},
		pause() {
			cancelAnimationFrame(this.rAF);
		},
		resume() {
			this.startTime = null;
			this.localDuration = +this.remaining;
			this.localStartVal = +this.printVal;
			requestAnimationFrame(this.count);
		},
		reset() {
			this.startTime = null;
			cancelAnimationFrame(this.rAF);
			this.displayValue = this.formatNumber(this.startVal);
		},
		count(timestamp) {
			if (!this.startTime) this.startTime = timestamp;
			this.timestamp = timestamp;
			const progress = timestamp - this.startTime;
			this.remaining = this.localDuration - progress;

			if (this.useEasing) {
				if (this.countDown) {
					this.printVal = this.localStartVal - this.easingFn(progress, 0, this.localStartVal - this.endVal, this.localDuration);
				} else {
					this.printVal = this.easingFn(progress, this.localStartVal, this.endVal - this.localStartVal, this.localDuration);
				}
			} else {
				if (this.countDown) {
					this.printVal = this.localStartVal - (this.localStartVal - this.endVal) * (progress / this.localDuration);
				} else {
					this.printVal = this.localStartVal + (this.endVal - this.localStartVal) * (progress / this.localDuration);
				}
			}
			if (this.countDown) {
				this.printVal = this.printVal < this.endVal ? this.endVal : this.printVal;
			} else {
				this.printVal = this.printVal > this.endVal ? this.endVal : this.printVal;
			}

			this.displayValue = this.formatNumber(this.printVal);
			if (progress < this.localDuration) {
				this.rAF = requestAnimationFrame(this.count);
			} else {
				this.$emit('callback');
			}
		},
		isNumber(val) {
			return !isNaN(parseFloat(val));
		},
		formatNumber(num) {
			num = num.toFixed(this.decimals);
			num += '';
			const x = num.split('.');
			let x1 = x[0];
			const x2 = x.length > 1 ? this.decimal + x[1] : '';
			const rgx = /(\d+)(\d{3})/;
			if (this.separator && !this.isNumber(this.separator)) {
				while (rgx.test(x1)) {
					x1 = x1.replace(rgx, '$1' + this.separator + '$2');
				}
			}
			return this.prefix + x1 + x2 + this.suffix;
		},
	},
	destroyed() {
		cancelAnimationFrame(this.rAF);
	},
};
</script>
